Generally, in the construction equipment or the industrial equipment, a hydraulic cylinder and the like used for operation are disposed, in addition, hydraulic motors are disposed on left and right sides of a lower running body, and the hydraulic motors are used as driving motors. According to the driving motor, pressurized oil is supplied from an oil pressure source or pressurized oil from the driving motor is discharged by controlling a driving direction-control valve. With this configuration, it is possible to control the running state of the lower running body on a road.
The construction machinery or the industrial machinery is provided with a cab for defining a driver's room in a frame on the lower running body, and an operating lever device for running is provided on a floor of the cab. If an operator inclines an operating lever for running back and forth, the switching of a running direction-control valve is controlled, and a rotation direction and a rotation speed of the driving motor are controlled. The speed of a vehicle running forward and backward and turning motion of the vehicle can be controlled in accordance with an inclining operation amount of the operating lever.
Such an operating lever device is provided with damper means which generates a resistance force at the time of inclination operation of the operating lever so as to enhance the operator's operation feeling. An operating lever device (see patent document 1 for example) using a rotary damper means is proposed as the damper means.
In the operating lever device described in the patent document 1, as shown in FIG. 10, rotary dampers 52 are inserted through projecting ends of turning shafts 51 projecting from a lever holder 50, and damper cases 53 of the inserted rotary dampers 52 are fixed to the lever holder 50. The rotary damper 52 is disposed between a side surface of the lever holder 50 and a bracket portion 54b of the operating lever 54. An annular damper chamber is defined in the damper case 53. Viscous fluid such as highly viscous oil is accommodated in the damper chamber, and a rotor 55 which is rotated against the viscous fluid is provided in each damper chamber.
Operating transmission lever 56 for transmitting the inclining operation amount of the operating levers 54 to the rotors 55 are provided between the rotors 55 of the rotary dampers 52 and the operating levers 54. If the turning shafts 51 are rotated by inclining operation of the operating levers 54, the rotors 55 also rotate in the same direction. The damper cases 53 are fixed to the lever holder 50, so the damper cases 53 do not rotate even if the operating levers 54 are inclined.
With this configuration, if the turning shafts 51 are rotated by inclining operation of the operating levers 54, the rotors 55 of the rotary dampers 52 together with the turning shaft 51 in unison against the viscous fluid in the damper chambers. With this, a resistance force caused by the viscous fluid is transmitted to the operating levers 54 as a reaction force, and an operator can obtain excellent operation feeling.
In the operating lever device described in the patent document 1, the rotors 55 are provided concentrically with the rotation shafts 51. That is, the inclining operation amount of the operating lever 54 and the rotation amount of the rotor 55 have a one-one relation. Thus, even if the rotor 55 is rotated as the operating lever 54 is inclined, only an intrinsic resistance force of the rotary damper 52 generated between the viscous fluid and the rotor 55 is received by the operating lever 54, and a resistance force received by the operating lever 54 can not be varied.
Due to this configuration, it is not possible to adjust the resistance force from the rotary damper 52 with respect to the inclining operation of the operating lever 54 in accordance with sensibility of the operator. In order to change the resistance force of the rotary damper 52 in accordance with the sensibility of the operator, it is necessary to prepare a plurality of rotary dampers having different resistance forces, and to selectively dispose the rotary dampers having a resistance force required by the operator. Even in this case, the rotary dampers must be replaced after the operating lever is detached, and the replacement operation can not be carried out easily. It is also difficult to select one of the plurality of rotary dampers that is most suitable for the operator's sensibility.
Patent document 1: Japanese Patent Laid-open Publication No. 2001-265455